The major objective of the project is to identify the host factors associated with resistance to dental caries. The strategy is to examine groups of subjects representing the extremes of caries activity, focusing on caries resistant (CR) adults with a DMF of O despite demonstrated dietary challenge and comparing them with age and sex matched caries susceptible (CS), with a DNF greater than 15. Comparative parallel examination of separately collected salivary fluids, plaques and pellicle of known age will largely be concerned with those factors that can modify: a) the nature of the bacterial flora, bacterial adherence, growth or acid production or, b) the net generation of acid. Specific parameters to be examined will include: a) specific IgA antibody, lysozyme, lactoferrin and lactoperoxidase, b) calcium binding proteins, c) cationic "permselectivity" proteins. Spectrum of acids and bases formed in plaque after sucrose challenge will be studied with and without access to saliva and in model systems in which plaques from CS are incubated with CR saliva and vice versa. Genetic implication of any differences noted betwen CR and CS will be studied in families of our cases.